286 E. NEWTON HARVEY. 



The colony is non-luminous except when stimulated. Then a 

 yellow greenish light appears of a more yellow hue than &quorea. 

 If the polyps are gently rubbed, a luminous slime comes off and 

 the secretion can be seen in the sea water. The polyps, ground 

 in sea water with sand, give a luminescent secretion which 

 becomes very brightly luminescent on addition of fresh water, 

 saponin and other cytolytic agents. The extract behaves exactly 

 as a similar one prepared from Cavernnlaria and already described 

 (2). In every way the behavior of Ptylosarcus agrees with that 

 of Cavernularia. 



It was impossible to demonstrate the presence of luciferin or 

 luciferase in Ptylosarcus. The following "crosses" were also 

 made, using extracts, which, from mode of preparation, should 

 have contained Ptylosarcus luciferin and luciferase. 



Plylosarcus luciferase X Ptylosarcus hiciferin negative. 

 Plylosarcus luciferase X ^Zquorea luciferin negative. 1 

 sEquorea luciferase X Ptylosarcus luciferin negative. 

 Cypridina luciferase X Ptylosarcus luciferin negative. 

 Ptylosarcus luciferase X Cypridina luciferin negative. 



Ptylosarcus brought into a dark room from direct sunlight was 

 observed to luminesce on immediate stimulation and as brightly 

 as at night. There is no inhibitive influence of light in this 

 form. 



EXPERIMENTS ON A SPONGE, Grantia. 



The question of luminosity in sponges is in rather of an un- 

 settled state. Some observers have reported luminescence but 

 Dahlgren (3) was inclined to attribute the light of a sponge 

 obtained at Naples to luminous worms and protozoa living in 

 its canals. 



At Friday Harbor there exists a sponge, Grantia sp.?, one to 

 three inches long, common on logs, piles, etc., in the sea water. 

 If rubbed, a yellowish luminescence may be observed which can 

 be obtained from all parts of the organism. If the sponge is 

 crushed the luminescence is quite bright. Every individual of 

 this kind of sponge examined showed luminescence, whereas 

 another sponge, Esperella 'sp.?, living on Pecten shells, was not 

 luminous. A few isolated dots of light only appeared on rubbing. 



1 Sometimes a faint light was observed whose significance is unknown. 



